As shown in FIG. 1, in a wireless communications system, a serving general packet radio service support node (Serving GPRS Supporting Node, SGSN) in a core network (CN) is configured to implement functions such as routing and forwarding, mobility management, session management, and user information storage in a general packet radio service (GPRS) or Universal Mobile Telecommunications System (UMTS) network. A gateway general packet radio service support node (GGSN) is configured to connect to an external packet data network (PDN).
In a network architecture shown in FIG. 1, user equipment (UE) initiates an attach requesting procedure by using a universal terrestrial radio access network (UTRAN) or a GSM/EDGE radio access network (GERAN). After completing UE authentication according to user subscription data and authentication data that are obtained from a home location register (HLR), the SGSN notifies the UE that attach is allowed.
When the UE needs to use a user service, the UE sends a request to the SGSN to establish a Packet Data Protocol context (PDP context). The SGSN finds an associated GGSN according to an access point name (APN) in the user subscription information, and requests the GGSN to add a PDP context. After receiving the request for adding a PDP context, the GGSN returns to the SGSN an IP address and a GPRS Tunneling Protocol (GTP) tunnel endpoint identifier (TEID) that are assigned to the UE. The SGSN returns to the UE a message that the PDP context is successfully established, and instructs the UTRAN or the GERAN to establish a corresponding radio air interface bearer to transmit user data.
After passing through the UTRAN/GERAN and the SGSN, uplink data of the UE is forwarded by the GGSN to a corresponding PDN. Downlink data from the external PDN is transmitted by the GGSN to an SGSN of the UE through a corresponding GTP tunnel according to the IP address of the UE, and is then sent to the UE by the SGSN by using the GERAN/UTRAN.
Referring to FIG. 2, an evolved network developed at the 3GPP specification release (R) 8 stage includes an evolved universal terrestrial radio access network (E-UTRAN), which may be also considered as a type of a radio access network RAN and is configured to implement a wireless function related to an evolved network. A mobility management entity (MME) is responsible for mobility management of a control plane, including management on a user context and mobile state, allocation of a temporary mobile subscriber identity (TMSI), or the like. A serving gateway entity (S-GW) is a user plane anchor between 3GPP radio access networks (such as an E-UTRAN, a UTRAN, and a GERAN). A packet data network gateway entity (P-GW) is a user plane anchor between a 3GPP radio access network and a non-3GPP radio access network, and provides an interface with an external PDN.
In the evolved network shown in FIG. 2, after accessing the E-UTRAN by using a radio air interface, UE is first attached to the MME; after the MME completes UE authentication according to user subscription data and authentication information that are obtained from a home subscriber server (HSS), the UE or the MME initiates a procedure of establishing a bearer used to transmit user data. The MME instructs the S-GW to establish the bearer for the UE, and the S-GW establishes for the UE a bearer from the E-UTRAN to the P-GW used to transmit user data. The P-GW forwards, to the UE by using the established bearer, downlink data from the external PDN, and forwards, to the PDN, uplink data from the UE.
As shown in FIG. 2, to be compatible with the existing UTRAN and GERAN, the UE may alternatively access the MME by using the UTRAN or the GERAN, and an SGSN, and may establish a GTP tunnel connection to the S-GW by using the UTRAN/GERAN and the SGSN. The S-GW converts the GTP tunnel into a corresponding P-GW-connected bearer that is used to transmit user data. The UTRAN may alternatively establish a GTP tunnel directly connected to the S-GW.
In a network architecture shown in FIG. 2, the MME is a network element that processes only control plane signaling. The S-GW and the P-GW may be combined into one network element, generally collectively referred to as a gateway.
In the network architectures shown in FIG. 1 and FIG. 2, the S-GW, the P-GW, and the GGSN may be collectively referred to as a gateway which is used as an interface between a radio access network and an external PDN to implement user data forwarding.
For a network architecture in which a control plane and a user plane of a gateway are separate, refer to FIG. 3. A gateway is divided into a user plane gateway (GW-U) and a control plane gateway (GW-C).
Referring to FIG. 3, UE accesses a wireless communications system shown in FIG. 3 by using a radio access network. The radio access network is connected to an MME/SGSN and a GW-U. A GW-C is connected to the MME/SGSN and may be configured to perform session management, IP address assignment, and the like. The GW-U is configured to forward user data. The GW-U forwards, to a PDN, user data from the radio access network, and forwards, to the radio access network, user data from the PDN.
The GW-C may be referred to as a control plane gateway, or may be referred to as a gateway controller, a control node, or a control gateway.
The GW-U may alternatively be referred to as a packet data forwarding gateway, a routing forwarding node, or a switch node.
Currently, in an architecture shown in FIG. 3, the GW-U needs to process user data according to a control message of the GW-C. This lacks flexibility.